1. Field of the Invention
The present invention relates generally to automated storage libraries for storing and retrieving computer data, and more particularly to systems and methods for improving the positional accuracy of library robotics through the use of parallax viewing techniques.
2. Description of the Related Art
A popular device for the handling and storage of large amounts of information in a data processing system is an automated storage library system, which generally improves the access speed and reliability of data storage libraries containing large amounts of information. Automated storage library systems typically include a plurality of storage media devices, a transport mechanism, and one or more storage media drives in communication with a computer system or network for inputting and outputting desired information to and from the plurality of storage media devices.
Magnetic tape cartridges, for example, have proven to be an efficient and effective medium for data storage in computer systems and storage libraries. Automated tape cartridge libraries generally have a plurality of storage bins or slots for storing tape cartridges, a robotic picker mechanism (often referred to as a “picker”), and one or more tape drives. The robotic picker may be controlled to select a specific storage tape cartridge from the library and transfer the tape cartridge between a storage slot and a tape drive within seconds. The robotic picker typically includes a gripper or hand mechanism positioned on the robotic picker. The robotic picker may position the gripper near a desired tape cartridge such that the gripper may grip the tape cartridge to remove the tape cartridge from the storage bin and transfer the tape cartridge to load the tape cartridge into a tape drive, load port (for adding or removing tapes from the library), or the like.
An automated storage library is typically interfaced to a computer system such as a computer network or the like. The storage library or interfaced computer system may index the location of the tape cartridges and their associated stored data within the storage library for later retrieval of the stored information. When desired, the storage library may be activated to retrieve a desired storage tape and load it into a drive to access the stored information and/or write new information. In large storage libraries multiple tape drives are generally employed to improve access and storage performance by operating in parallel as well as providing back-up drives in case of failure, maintenance, and the like.
As robotic mechanisms move tape cartridges between storage bins and tape drives the positional accuracy of the robotic mechanism in relation to the storage bins and tape drives is desirably maintained to a high degree to reduce the potential for wear and damage to the cartridges, storage bins, and tape drives. For example, inaccurate positioning may cause mating surfaces between storage cartridge, storage bins, and tape drives to rub or collide causing damage to one or more. Additionally, wear and collisions may cause undesirable debris within the automated library housing that may interfere with or degrade, for example, the tape drive operation.
Positional accuracy of the robotic mechanism may be determined with an optical scanner that scans a point of light in x and y directions, e.g., horizontally and vertically, across a target or fiducial mark on a storage bin or drive bezel. If the camera is positioned such that the target falls within the camera's field of vision, the x and y coordinate values may be measured directly. The distance in the z direction, the extension or depth of the target from the camera, however, is not directly measured by the camera. The distance or z coordinate value can be inferred from a combination of other measurable and/or previously known quantities. For example, the distance may be determined by comparing the image or apparent size of the target to the known size of the target.
One problem with conventional optical approaches for determining the distance between a robotic picker mechanism and portion of the library including a calibration mark is that the target size generally must be known. Additionally, if the calibration mark size is only approximately known, e.g., known within a certain variance, the distance measurement suffers in proportion to the variance of the calibration mark size.
Therefore, new methods and systems for determining positional accuracy of a robotic mechanism in an automated storage library are needed. Further, methods and systems for determining positional accuracy with greater accuracy and/or smaller fiducial marks than prior approaches are desired.